1. Technical Field
The present disclosure relates to an airbag device, particularly, to an airbag device having an airbag body that inflates and deploys between a leg of a seated person and the floor panel of a vehicle.
2. Related Art
In some collisions a force is applied to a leg of a passenger due to an impact at the time of a collision of a vehicle, the force including a vehicle width direction moment (hereinafter also referred to as a transverse moment) Mx, a vehicle fore-and-aft direction moment (hereinafter also referred to as a fore-and-aft moment) My, and an axis direction load (hereinafter also referred to as an axial load) Fz. As a result, the leg is thrown in an unexpected direction and damaged.
In order to protect a leg against the above-mentioned moments and the axial load, there are known techniques that protect the leg by inflating an airbag at the time of a collision.
For example, Japanese Unexamined Patent Application Publication (JP-A) No. 11-11242 discloses a technology in which a stopper member for receiving the heel of a foot of a seated person is formed by an airbag. The stopper member is placed on the floor surface of a vehicle cabin to protect the heel from being pushed into between an operating pedal and the floor panel due to the moment My caused by an impact of a collision.
For another example, an airbag device disclosed in Japanese Unexamined Patent Application Publication (JP-A) No. 2008-254523 includes an airbag having a. The heel rest base is disposed on the floor of a vehicle forwardly of a front seat and, both heels of a passenger seated on the front seat are placeable on the heel rest. The airbag device is capable of preventing dorsiflexion and twist of the ankles of the seated passenger by inflation of the airbag.
It is known that an impact load at the time of a head-on collision of a vehicle occurs in two stages for an initial load and a latter load. That is, an initial load is caused by an inertial force that is generated by a collision, and the latter load is caused by deformation of the vehicle body, such as rearward movement of a toe board. FIG. 4 is a schematic graph illustrating the two stage load.
Here, an inertial force is applied to the legs of a seated person due to a load F1 in the first stage at time t=t1, and thus a high axial load Fz occurs. In addition, a so-called lift up phenomenon is induced in which a latter load F2 in the second stage at time t=t2 causes deformation of the vehicle body, and thus a high vehicle fore-and-aft direction moment My to a foot causes a corresponding leg to be thrown forward on the floor panel in the vehicle body.
Although the technology of JP-A No. 11-11242 is capable of preventing a foot from being caught between the floor panel and the operating pedal, only the central portion of the bottom surface of the foot is buffered by an airbag, and a buffering effect for protecting the leg from the above-mentioned axial load Fz is not sufficiently obtained. Furthermore, the disclosure of JP-A No. 11-11242 does not provide the effect of protecting the leg from lift up of the floor panel due to the vehicle fore-and-aft direction moment My.
The technology described in JP-A No. 2008-254523 protects a heel with the heel rest base, and thus an effect for protecting the leg from the axial load Fz is obtained to some extent. However, no approach is made at all to prevent the lift up of the floor panel due to the vehicle fore-and-aft direction moment My.